Dennis Kerrison, 69, of Chertsey, Surrey, was sentenced to four years in prison, Paul Jennings, 57, of Neston, to two years, and Miltiades Papachristos, 51, of Thessaloniki, Greece, to 18 months.

David Turner, 59, of Newmarket, Suffolk, was given a 16-month suspended sentence with 300 hours' unpaid work.

The SFO said that Kerrison and Papachristos were convicted in June of conspiracy to commit corruption.

Jennings pleaded guilty in June 2012 to two charges of conspiracy to commit corruption and the following month to a further similar charge.

Turner pleaded guilty in January 2012 to three charges of conspiracy to commit corruption Judge Andrew Goymer said: "Corruption in this company was endemic, institutionalised and ingrained... but despite being a separate legal entity, it is not an automated machine; decisions are made by human minds.

"None of these defendants would consider themselves in the same category as common criminals who commit crimes of dishonesty or violence... but the real harm lies in the effect on public life, the effect on community and in particular with this corruption, its effect on the environment.

"If a company registered or based in the UK engages in bribery of foreign officials, it tarnishes the reputation of this country in the international arena."

David Green, director of the SFO, said: "This successful conclusion to a long-running investigation demonstrates the SFO's ability and determination to bring individuals committing crimes in the corporate arena to justice."

Innospec itself pleaded guilty in March 2010 to bribing state officials in Indonesia and was fined 12.7 million dollars (£7.5 million) in England with additional penalties being imposed in the US.

The SFO said Kerrison and Papachristos were convicted of conspiracy to commit corruption in relation to Indonesia only.

It said Jennings and Turner both pleaded guilty to conspiracy to commit corruption in relation to Indonesia and Iraq.